1. Field of the Invention
The present invention relates to a bilayer membrane device, for example, to a bilayer membrane device having a bilayer membrane which is constructed of two molecular layers (i.e. monolayers) and holds protein or the like and has a constitution similar to that of an organic cell membrane, and having excellent stability that enables it to be used when causing a held protein to function within a bilayer membrane or during measurement of that function.
2. Description of the Related Art
Various proposals have been made in the past for producing a bilayer membrane having a constitution similar to that of an organic cell membrane. Protein function research has been conducted in which protein is caused to function in the same manner as in a cell membrane by using this bilayer membrane. Moreover, bio-functional device are expected to be produced that utilize the functions of bilayer membrane and proteins.
In the case of devices having an artificial bilayer membrane that have been reported in the past, monolayer is used that is composed of polar groups and hydrophobic groups. In an aqueous solution, a Teflon substrate in which a hole is provided in the center is arranged upright as shown in FIG. 1, and two layers of monolayer lipid membranes are formed in the hole portion of this Teflon substrate with the polar groups facing to the outside and hydrophobic groups facing to the inside as shown in FIG. 2, resulting in the constitution of a bilayer membrane.
However, since the bilayer membranes produced in this manner are adhered only by their mutual intermolecular forces, the bilayer membrane structure ends up being quickly destroyed due to impact or other excessive outside forces. In addition, even when allowed to stand undisturbed, there is the problem of bilayer membrane structures like those shown in the drawings only being maintainable for several hours.
With this in mind, it has been proposed to form a bilayer membrane on the surface of support substrate for the purpose of producing a bilayer membrane having higher stability. In the example shown in FIG. 3A, the polar groups of one of the lipid monolayer are adsorbed onto a support substrate 3 made of glass or such material arranged horizontally in an aqueous solution to form monolayer membrane 2. Moreover, a second layer of monolayer membrane 2 is formed on this monolayer membrane 2 by adsorbing lipid single molecules to obtain a bilayer membrane.
In addition, in another example, stearylmercaptan, for example, is introduced onto the surface of substrate 6 formed by Au as shown in FIG. 3B, after which alkanethiol monolayer membrane 4 is formed on the substrate surface by Au--S bonding. Monolayer lipid membrane 2 is further adsorbed onto the resulting monolayer membrane 4 to form a bilayer membrane.
However, even in the case of a bilayer membrane formed by using a support substrate as described above, the length of time during which its bilayer membrane structure can be maintained when allowed to stand undisturbed in an aqueous solution is only in the range of several hours to just over ten hours. Thus, it is difficult to perform processing such as inserting protein into the resulting bilayer membrane, thus causing this membrane to lack practicality as a device. Consequently, there is a need to obtain a bilayer membrane having even greater stability.